Since 1966 this cross-national project has had psychiatrists and other team members from the social, psychological and statistical sciences based in New York and London. Studies are concerned with differences between the United States and the United Kingdom in diagnostic practice, in the frequency and type of mental disorder and in patterns of mental health care. An important part of this work is the development of reliable and valid methods of classifying patients in both countries and the interchange between the two countries of videotaped interviews. Between 1966 - 1970 the studies included only patients in public mental hospitals from the age range 20-59 years. During 1971-1972 the team focuses on geriatric patients with special reference to the distinction between, and the prognosis of, the organic and the affective disorders.